Michel Meyer

Evaluation of coupled reactive distillation performances by means of a rigorous simulation procedure

Publisher Summary This chapter discusses the non equilibrium model (NEQ) for multicomponent separation processes, including liquid and/or gas reactions. This model includes the finite mass-transfer rate described by Maxwell–Stefan equations. The bulk of both the vapor and liquid are perfectly mixed, and the resistance to mass and heat transfer is located in two films at the liquid/vapor interface (film theory). There are no restrictive hypotheses as to the nature and the localization of the chemical reactions. The chapter describes the original formulation of mass transfer and solves it to avoid the bootstrap problem. The resulting differential algebraic equations (DAEs) system is then solved. The chapter presents the resolution and focus on two keys points: the coherent initial state and the reduction of differentiation index. With several examples, a comparison between equilibrium stage model (EQ) and the NEQ model is affected and a sensitivity analysis is done to highlight the importance of the film thickness.

Dynamics of reactive distillation for the production of ethyl acetate: experiments at a pilot plant and modelling

Abstract In order to understand the complex behaviour of the reactive distillation process and to be able to provide an accurate design of a reactive column, detailed analyses on both continuous and transient regime become necessary. The objective is the definition of a reliable simulation model, based on experimental data obtained from a real pilot-scale plant device for the heterogeneously catalysed esterification of acetic acid and ethanol to form ethyl acetate and water. The choice of the parameters for the continuous equilibrium model was discussed and the simulation results provided good agreement with experimental data, revealing an interesting sensitivity of the catalyst activity to the feed composition. Once column configuration and operational parameters were validated, dynamic experiments were realized so as to interpret the sensitivity of different disturbances. Feed flow rates, reflux ratio and heat duty were perturbed and the consequent open loop transient responses were identified. The assessment of hydrodynamic parameters and the validation of the transient data allow the definition of a reliable dynamic model that represents tendencies and behaviours of the process well. The resulting model is to be applied into a more complex controllability methodology.

Recovery of succinic acid in fermentation broth via reactive LL extraction: effect of chemical kinetics and solvent choice

In this paper, a study of kinetics effects on the reactive liquid-liquid extraction column is proposed. In a first part, design parameters of reactive liquid-liquid extraction column are derived from a method proposed by Mizzi (2016). In a second part, using a kinetic model, the performances of the column are studied with different configuration and design parameters. This study allows a comparison of the performances of the column in terms of conversion rate, recovery rate and purity. For the chosen examples, the kinetic limitation is very strong. So the unit operations of reactive liquid-liquid extraction with a high retention capacity will be privileged: a cascade of decanter mixers. In conclusion, this article shows that the choice of solvent and the parameters of the column as the solvent flowrate, the number of theoretical stage, liquid hold up or kinetics of the reaction have an important influence on the performances of the column and sometimes on the feasibility of the separation.

Production Zone Method: a New Non-ideal Shortcut Method for Distillation Column Design

Graphical shortcut methods are useful tools for the design of distillation columns. The proposed nonideal shortcut method includes a graphical representation and is based on the concept of operation leaves. This new method uses a production segment rather than a completely specified product, which eliminates any sensitivity to the composition of the minor product. Concerning phase equilibria, no restrictive assumptions are made. The study aimed (1) to determine whether a specified separation respects the mass balance and thermodynamic feasibility and (2) to find the minimum reflux ratio for a preliminary design of the column. Designs obtained with this new method for ideal, non-ideal, and azeotropic mixtures give purity and recovery rates close to the specifications, which might be impossible to obtain with a conventional ideal shortcut like the well-known Fenske–Underwood–Gilliland shortcut method. The distillation boundaries of azeotropic mixtures are taken into account thanks to a non-ideal thermodynamic model applied to the calculation, which is not the case with a conventional ideal shortcut. The paper examines the following mixtures: an ideal mixture of ethanol, n-propanol, and n-butanol; a non-ideal mixture of acetone, water, and acetic acid; and an azeotropic mixture of acetone, isopropanol, and water.